The invention concerns a circuit arrangement for compensation of attenuation in an antenna lead for a mobile wireless device.
For example, in motor vehicles, mobile wireless devices are operated with an antenna arranged externally on the vehicle, due to the shielding effect of the automobile body. The mobile wireless device, for example, a mobile telephone held by a hands-free device is connected with the external antenna via an antenna lead (HF cable) for this purpose. Even if the reception and the possibilities of transmission are clearly improved by the use of external antennas when compared to operation without external antennas, it can be viewed as a disadvantage that the signals that are transmitted and received are subject to attenuation in the antenna lead. Therefore, according to solutions that have become known in practice, the antenna lead is guided via special circuit arrangements accommodated between the mobile wireless device and the external antenna for compensation of the attenuation occurring in the antenna lead. Such a circuit arrangement is described, for example, in DE 195-36,640. Since different frequency ranges are used in the mobile wireless device for uncoupling signals that are transmitted and received within one frequency band which is used for transmission and reception, and for an optimal compensation of the occurring attenuation, the circuit arrangement presented in the document provides separate signal pathways for transmitted and received signals. Each time depending on whether an HF signal is received or transmitted by the mobile wireless device, either the transmission or reception pathway is activated by a special HF reversing switch, so that the signal is guided either over a power or transmission amplifier or over a special reception or low-noise amplifier.
Another solution has become known through DE 199-13,064. The compensation circuit described in this document is designed for dual-band operation. It thus provides frequency band filters on the input and output sides, by means of which, the HF signals are introduced into the circuit component provided for the respective frequency band. Depending on a transmission signal recognized by a detection circuit, by means of a special circuit arrangement, the transmission amplifier is turned on for the respective frequency band and the appropriate signal pathway is activated. Developments, in which advantages that are known, among other things, for improved utilization of frequency bands and for profitting from the different mobile wireless systems existing at the present time, have recently occurred, and more flexible transmission methods will be achieved in future mobile wireless systems. Thus, for example, the frequency ranges provided for transmitting and receiving can be alternated within one frequency band, unlike what is known from GSM networks. In addition, transmission may occur selectively in an existing telecommunications connection, controlled by time slots, or as a continuous wave (continuous transmission without dividing into time slots).